This invention relates to an arm structure for an injecting molding machine, particularly to one moved by an oil pressure cylinder injecting molding machine positioned between a receiving disc and a movable mold base, never colliding with the oil pressure cylinder when the arm structure retreats inward.
A common known conventional arm-style injecting molding machine includes an arm structure 30 as shown in FIG. 5, pivotally connected between a movable mold base 10 and a receiving disc 20. The arm structure includes a first arm 301, a second arm 302, and a third arm 303 mutually and pivotally connected with each other. Further, the first arm 301 is pivotally connected onto a cress-shaped head 304 and then also pivotally connected to the second arm 302, which has one end pivotally connected to the receiving disc 20 and the other end pivotally connected to the third arm 303. The other end of the third arm 303 is pivotally connected to the movable mold base 10. The oil pressure cylinder 40 fixed on the receiving disc and extending outward has its piston rod 401 connected firmly on the cross-shaped head 304. Then the oil pressure cylinder 40 operates to move the movable mold base 10 to open and close the mold.
However, as the oil pressure cylinder 40 extends out of the machine body, it takes a large space whether in transporting or installing, especially in installing, the oil pressure cylinder occupies a large space of a factory, causing a problem in arranging working place and the injecting molding machine. So, some makers have tried to position the oil pressure cylinder for moving the arm structure between the receiving disc and the movable mold base. However, the space between the receiving disc and the movable mold base is limited so the pivotal joint of the second arm collides with the oil pressure cylinder body extending in the receiving disc when the arm structure retreats inward. Besides, a smaller oil pressure cylinder cannot be used because of mold closing force being not enough, in order to avoid operating radius of the joint of the second arm.
The invention has been devised to offer an arm structure for an injecting molding machine, having an oil pressure cylinder positioned between the receiving disc and the movable mold base. A second arm and a third arm are formed with plural pivotal plates, which are pivoted with the fix plate of the receiving disc and the movable mold base. The two inner pivotal plates of the second arm are located in the two sides of the cylinder with a space a little larger than the outer diameter of the oil pressure cylinder. In addition, the space between the two joints pivotally connected between the second and the third arms are also a little larger than the outer diameter of the coil pressure cylinder. Therefore, The joints between the second and the third arm can pass through without colliding with the oil pressure cylinder, when the arm structure retreats, in opening the mold and subsequently closing the mold. Thus, the oil pressure cylinder can be positioned inside the receiving disc, reducing the dimensions of an injecting molding machine for transportation and installation of the injecting and molding machine.